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| Forget me not How we bond with our
nearest and dearest IT'S hard to believe we could fail to
recognise people with whom we've been intimate. Yet geneticists
in the US have created socially inept rodents with just that failing.
They provide the clearest picture yet of how a molecule popularly
known as the "love hormone" shapes relationships in mammals. In
animals as different as mice, voles, monkeys and humans, the hormone
oxytocin is released from the brain when relationships are being
forged, such as during mating or maternal nurturing. But just
what oxytocin does has been difficult to work out. When injected
into an animal, for example, the hormone can impair or promote
bonding, depending on how it is given. Now James Winslow of Emory
University in Atlanta and his colleagues have provided strong
evidence that oxytocin promotes "social memory"--the development
of familiarity between individuals. When male mice encounter a
female, they routinely sniff the newcomer to determine whether
she is an appropriate mate. If normal males are repeatedly exposed
to the same female at intervals of a minute, this period of exploration
shortens with each encounter, from 40 seconds to just 10 seconds
on the fourth meeting. But males genetically engineered to lack
oxytocin behave quite differently. The female gets the full 40-second
scrutiny on each encounter, says Winslow. "Each time, he acts
like he has never seen her before." The defect seems to be restricted
to the social realm. The mice without oxytocin react normally
to other smell cues and can learn to navigate mazes, showing their
perception and general memory are intact. And a dose of oxytocin
quickly cures them of their indifference to old acquaintances.
Geert De Vries, a neuroscientist at the University of Massachusetts,
Amherst, says the results are very convincing. "We know very little
about how social recognition works in any species," he says. He
believes the study will stimulate new thinking about the issue.
Source: (Nature Genetics, vol 25, p 284) |
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